Switched DC DC converters comprise a switched power stage, wherein an output voltage is generated according to a switching signal and an input voltage. The switching signal is generated in a control circuit that adjusts the output voltage to a reference voltage. The switched power stage comprises a dual switch consisting of a high-side field effect transistor (FET) and a low-side FET, an inductance and a capacitor. During a charge phase, the high-side FET is turned on and the low-side FET is turned off by the switching signal to charge the capacitor. During a discharge phase the high-side FET is turned off and the low-side FET is turned on to match the average inductor current to the load current. The switching signal is generated as digital pulse width modulation signal with a duty cycle determined by a control law. The control law may be implemented by a PID compensator.
Many DC DC converters also have light mode to have better efficiency when the load runs at lower currents. In light mode instead of generating the switching signal in a digital control path the switching signal is generated by a feedback loop with a constant-on-time comparator. However, if the load current increases to normal levels there is the problem to come back to normal operation (the high load mode) without generating an unreasonable overshoot of the output voltage.
Therefore, what is needed is solution that avoids an unreasonable overshoot of the output voltage when transitioning from light load mode to high load mode.